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This invention relates to semiconductor diode lasers, or more specifically to a semiconductor diode laser called a (VCSEL) xe2x80x9cVertical Cavity Surface Emitting Laserxe2x80x9d, which is a device that uses a process known as recombination radiation to produce laser-light emissions. These semiconductor diode lasers have vertical cavities, which amplify into laser emissions the photonic radiation produced by a double-heterostructure active-region. Comprised, as a multilayered vertical structure, having a substrate, an electronic and optically pumped double-heterostructure light-emitting diode active-region, and two feedback-providing contra-positioned light-reflecting structures defining a resonant cavity.
Currently, VCSELs use, as their main photon producing structures a single double-heterostructure light emitting diode active-region. Typically, a double-heterostructure xe2x80x9cLight Emitting Diodexe2x80x9d (LED) is constructed from latticed-matched extrinsic semiconductor binary materials like (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d, (InP) xe2x80x9cIndium-Phosphidexe2x80x9d, and (GaSb) xe2x80x9cGallium-Antimonidexe2x80x9d. Additionally, a double-heterostructure LED can also be constructed from latticed-matched extrinsic semiconductor ternary materials like (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d, or constructed from latticed-matched extrinsic semiconductor quaternary materials like (InGaAsP) xe2x80x9cIndium-Gallium-Arsenic-Phosphidexe2x80x9d, and (InGaAsSb) xe2x80x9cIndium-Gallium-Arsenic-Antimonidexe2x80x9d. Typically, a single double-heterostructure LED active-region will contain either a xe2x80x9cSingle Quantum Wellxe2x80x9d (SQW) active-area (i.e., used in what is sometimes called a SQW laser), which is constructed from a single extrinsic semiconductor material, or a xe2x80x9cMultiple Quantum Wellxe2x80x9d (MQW) active-area (i.e., used in what is sometimes called a MQW laser), which is constructed from several extrinsic semiconductor materials.
In addition, recombination produced optical-radiation emitted by current VCSELs is far from ideal. For example, the coherence properties of recombination radiation emissions produced by prior-art VCSELs is most often of poor quality, with their coherence measured to be somewhere between the laser radiation emitted by a low-pressure gas laser and an incoherent line-source. Additionally, the recombination radiation produced emissions created by prior-art VCSELs is not collimated, but divergent having a total divergence of about xe2x80x9c30xe2x80x9d degrees from a VCSEL emitter""s top-surface edge. Generally, all prior-art VCSEL designs use a cavity-external and microscopic collimating lens to correct the problem of laser beam divergence. Adjustment of a VCSEL""s divergent light-rays into collimated and parallel traveling light-rays is accomplished when a cavity-external collimating lens has been located several microns from a VCSEL emitter""s top horizontal surface.
Furthermore, to correct current VCSEL laser beam incoherence and laser beam divergence problems a new type of VCSEL design is required. Therefore, any problems presented above are substantially solved by the present invention, while any purposes presented above arc realized as well in the present invention""s Phase Conjugated Vertical Cavity Surface Emitting Laser design, which is described in greater detail within the preferred embodiments written below.
In accordance with the present invention, a Phase Conjugated Vertical Cavity Surface Emitting Laser comprises a cavity folding corner-cube shaped prism waveguide having three internal reflecting prisms that provide a cavity folding transverse redirection, polarity stabilization, and a retro-reflection of intracavity produced fundamental photonic radiation; four electrically unisolated double-heterojunction LED structures constructed from interference forming nonlinear semiconductor materials (e.g., Gallium-Arsenide, Indium-Gallium-Arsenide, and/or Aluminum-Gallium-Arsenide) that will provide electronic production, optical amplification, and phase conjugated reflection of intracavity produced fundamental photonic radiation; and a partial reflecting feedback providing mirror structure capable of reflecting a sufficient amount of undiffused intracavity produced optical radiation into the laser""s nonlinear and laser-active semiconductor material for further amplification, while providing an apparatus that produces frequency-selected output of wavelength-specific monochromic and amplified photonic radiation.
Accordingly, besides the objects and advantages of a phase conjugated vertical-cavity surface-emitting laser described in the above patent, several other objects and advantages of the present invention are:
(a) To provide a phase conjugated vertical-cavity surface-emitting laser that creates a high output of narrow-linewidth amplified light using a cavity folding internal reflecting corner-cube shaped prism waveguide comprised from a single layer of optically transparent material;
(b) To provide a phase conjugated vertical-cavity surface-emitting laser that is inexpensive to manufacture, because it has eliminated the expensive epitaxial deposition of a primary quarterwave mirror stack assembly comprised as an multitude of quarterwave thick epitaxial deposited alternating layers that are constructed from refractive opposing materials and replaced it with a single corner-cube shaped prism waveguide, which is constructed from a single inexpensive layer of sputter or epitaxially deposited optically transparent material;
(c) To provide a phase conjugated vertical-cavity surface-emitting laser that uses two graded confinement cladding-layers to generate higher-output of laser emissions;
(d) To provide a phase conjugated vertical-cavity surface-emitting laser, which produces a more effective output gain by using two graded confinement cladding-layers within each active-region to lower the heat produced by electrical resistance that occurs between current conducting contact-layers and their adjacent cladding-layers;
(e) To provide a phase conjugated vertical-cavity surface-emitting laser, which increases optical confinement with the addition of total internal reflecting cladding material to the surrounding vertical and outermost wall surfaces of the phase conjugated vertical-cavity surface-emitting laser""s folded vertical-cavity(s);
(f) To provide a phase conjugated vertical-cavity surface-emitting laser, which can be configured and controlled as a single phase conjugated vertical-cavity surface-emitting laser device;
(g) To provide a phase conjugated vertical-cavity surface-emitting laser, which can be configured as a single phase conjugated vertical-cavity surface-emitting laser-array comprising a multitude of phase conjugated vertical-cavity surface-emitting lasers, which can be controlled as a single group of phase conjugated vertical-cavity surface-emitting lasers or controlled as a single group of independently controlled phase conjugated vertical-cavity surface-emitting lasers;
(h) To provide a phase conjugated vertical-cavity surface-emitting laser or a phase conjugated vertical-cavity surface-emitting laser-array, which can be manufactured at the same time, as a single integrated semiconductor device, using the same semiconductor and substrate material used to construct the laser-array""s control-circuitry;
(j) To provide a phase conjugated vertical-cavity surface-emitting laser, which replaces a primary quarterwave mirror-stack assembly with a cornercube prism waveguide, if comprised of quartz or fused silica, will totally reflect one-hundred percent all frequencies of optical radiation that enters the waveguide""s top horizontally-flat front-face surface;
(k) To provide a phase conjugated vertical-cavity surface-emitting laser, which inexpensively constructs its corner-cube shaped prism waveguide using a well-known reactive ion-milling process to slice out the waveguide""s prism facet(s);
(l) To provide a phase conjugated vertical-cavity surface-emitting laser that can deposit a dielectric material like fused-silica onto any construction material that might be used to construct any frequency producing semiconductor diode or combination thereof that could possibly be used to construct a phase conjugated vertical-cavity surface-emitting laser or a phase conjugated vertical-cavity surface-emitting laser-array;
(m) To provide a phase conjugated vertical-cavity surface-emitting laser, which uses an amorphous material like xe2x80x9cLithium-Fluoridexe2x80x9d (LiF) to create an optical cladding-layer, which is deposited around each vertical-cavity or cavities of each phase conjugated vertical-cavity surface-emitting laser, creating a structure providing for the total internal reflection of intracavity produced light, thermal dispersive, and additional support to a phase conjugated vertical-cavity surface-emitting laser""s corner-cube prism waveguide structure(s);
(n) To provide a phase conjugated vertical-cavity surface-emitting laser, which increases its output, while maintaining a narrow line-width for its output emissions(s);
(o) To provide a phase conjugated vertical-cavity surface-emitting laser that can use an intracavity four-wave mixing geometry that promotes the production of distortion and dispersion free high-power laser output emissions;
(p) To provide a phase conjugated vertical-cavity surface-emitting laser that can use an intracavity six-wave mixing geometry that promotes the production of distortion and dispersion free high-power laser output emissions;
(q) To provide a phase conjugated vertical-cavity surface-emitting laser that uses two concave shaped active-regions and two planar shaped active-regions to successfully implement intracavity four-wave mixing to promote within the laser""s vertical-cavity the production of a phase conjugated mirror;
(r) To provide a phase conjugated vertical-cavity surface-emitting laser, which will produce an increase of nearly 15-mW to its output emissions;
(s) To provide a phase conjugated vertical-cavity surface-emitting laser, which increases gain to its laser emission output by using a nonlinear laser-active gain medium material like Gallium-Arsenide in the construction of its four active-region double-heterostructure LEDs.
Further objects and advantages are provided below for the present inventions phase conjugated vertical-cavity surface-emitting laser. While, the selection of one semiconductor or optical material over another for use in the construction of a PCVCSEL""s active-regions, corner-cube prism waveguide, and quarterwave mirror-stack assembly is not determined by any structural need or lattice compatibility, but is determined by a particular application""s need for laser output of a specific wavelength. The materials used in the construction of the present invention are presented here only as the preferred example of a group of several wavelength specific materials that might be used in the construction of the present invention""s wavelength transcendent multi-layered structures. A PCVCSEL""s novel features and un-obvious properties lay within its xe2x80x98phase-conjugatingxe2x80x99 structures, and because they can exist and/or can occur using different wavelength specific semiconductor and/or optical materials shows that the various structures that comprise a PCVCSEL have sufficient novelty and a non-obviousness that is independent of any one particular semiconductor or optical material that might or could be used in its construction.
Still further, objects and advantages will become apparent from a consideration of the ensuing description and drawings.
An additional object, used in the present invention is an internal reflecting corner-cube prism waveguide, which can be constructed, for example, from (SiO2) xe2x80x9cFused Silicaxe2x80x9d a material that retro-reflects xe2x80x9c100xe2x80x9d percent any optical radiation with a wavelength between xe2x80x9c150xe2x80x9d nanometers and xe2x80x9c4xe2x80x9d micrometers that enters its top front-face surface. A corner-cube prism waveguide is exactly what its name implies, a waveguide having the shape of a cube""s corner that is cut off orthogonal to one of its triad (i.e., body-diagonal) axes, which uses internal reflection as its means for redirecting optical radiation. Wherein, the front-face surface of the resultant prism waveguide would typically have the shape of the invention""s vertical-cavity, and plane-parallel to a PCVCSEL""s secondary reflector, which typically comprises of an epitaxially deposited quarterwave mirror-stack assembly constructed from optical materials of opposed refractive indices.
Moreover, as the result of three totally internal reflections, a corner-cube""s three prism facets form a waveguide that redirects any incident light-rays backward toward their original direction no matter what angle of incidence the previously mentioned light-rays had when they entered the front-face surface of the corner-cube prism waveguide. Retro-reflected light-rays are shifted laterally by an amount that depends on a light-ray""s angle of incidence and point of entry upon the front-face surface of the corner-cube prism waveguide. The location of the internal retro-reflecting corner-cube prism waveguide is at the base of a PCVCSEL""s vertical-cavity. Furthermore, not only does the corner-cube prism waveguide replace the primary quarterwave DBR mirror-stack assembly normally used in current prior-art VCSEL designs with a structure comprising of a single layer, but with a structure that also functions to stabilize the polarity of a PCVCSEL""s laser-light output emissions,
An additional object, used in the present invention is the symmetry and layout of a PCVCSEL""s four electrically un-isolated active-regions and the other layered materials that make up the rest of its vertical-cavity. It should be understood, however, that the process of intracavity four-wave mixing in the production of phase-conjugation and its distortion removing properties can be created using any wavelength of optical radiation made possible through existing semiconductor diode laser technologies.
Consequently, since the phase-conjugation process is independent of any particular wavelength of optical radiation it must also be independent of any particular wavelength determined material as well. Therefore, the choice between semiconductor materials used in a PCVCSEL""s construction is presented here only to show that the PCVCSEL""s design has sufficient novelty.
In addition, is a PCVCSEL""s first contact-layer, which is constructed from a highly p+doped (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d binary material, and located above the top outermost surface of the PCVCSEL""s corner-cube prism waveguide""s normal horizontal and circular front-face surface.
In addition, is a PCVCSEL""s first cladding-layer, which is constructed from a P-doped concentrically-graded (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s first contact-layer.
In addition, is a PCVCSEL""s first active-area (i.e., called pump 1), which is comprised either as a xe2x80x9cSingle Quantum Wellxe2x80x9d (SQW) constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d, or as a xe2x80x9cMultiple Quantum Wellxe2x80x9d (MQW) having six quantum wells constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d and seven quantum well cladding-layers constructed from (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d. The layers that makeup the active-area""s MQW are to be epitaxially deposited, one layer upon the other, using the top outermost surface of the PCVCSEL""s first cladding-layer to commence deposition.
In addition, is a PCVCSEL""s second cladding-layer, which is constructed from a concentrically-graded N-doped (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the last layer comprising the PCVCSEL""s first active-area (i.e., called pump 1).
In addition, is a PCVCSEL""s second contact-layer, which is comprised from a highly n+ doped (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d binary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s second cladding-layer.
In addition, is a PCVCSEL""s third cladding-layer, which is constructed from a concentrically-graded N-doped (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s second contact-layer.
In addition, is a PCVCSEL""s second active-area (i.e., called probe 1), which is comprised either as a xe2x80x9cSingle Quantum Wellxe2x80x9d (SQW) constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d, or as a xe2x80x9cMultiple Quantum Wellxe2x80x9d (MQW) having three quantum wells constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d and four quantum well cladding-layers constructed from (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d. The seven coplanar layers that makeup a active-area""s MQW are to be epitaxially deposited, one layer upon the other, using the top outermost surface of the PCVCSEL""s third cladding-layer to commence deposition,
In addition, is a PCVCSEL""s fourth cladding-layer, which is constructed from a concentrically-graded P-doped (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the last layer comprising the PCVCSEL""s second active-area (i.e., called probe 1).
In addition, is a PCVCSEL""s third contact-layer, which is constructed from a highly p+doped (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d binary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s fourth cladding-layer.
In addition, is a PCVCSEL""s fifth cladding-layer, which is constructed from a concentrically-graded P-doped (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s third contact-layer,
In addition, is a PCVCSEL""s third active-area (i.e., called probe 2), which is comprised either as a xe2x80x9cSingle Quantum Wellxe2x80x9d (SQW) constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d, or as a xe2x80x9cMultiple Quantum Wellxe2x80x9d (MQW) having three quantum wells constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d and four quantum well cladding-layers constructed from (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d. The seven coplanar layers that makeup an active-area""s MQW are to be epitaxially deposited, one layer upon the other, using the top outermost surface of the PCVCSEL""s fifth cladding-layer to commence deposition.
In addition, is a PCVCSEL""s sixth cladding-layer, which is constructed from a concentrically-graded N-doped (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the last layer comprising the PCVCSEL""s third active-area (i.e., called probe 2).
In addition, is a PCVCSEL""s fourth contact-layer, which is constructed from a highly n+doped (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d binary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s sixth cladding-layer.
In-addition, is a PCVCSEL""s seventh cladding-layer, which is constructed from a N-doped concentrically-graded (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s fourth contact-layer,
In addition, is a PCVCSEL""s fourth active-area (i.e., called pump 2), which is comprised either as a xe2x80x9cSingle Quantum Wellxe2x80x9d (SQW) constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d, or as a xe2x80x9cMultiple Quantum Wellxe2x80x9d (MQW) having six quantum wells constructed from (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d and seven quantum well cladding-layers constructed from (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d. The thirteen layers that makeup an active-area""s MQW are to be epitaxially deposited, one layer upon the other, using the top outermost surface of the PCVCSEL""s fourth cladding-layer to commence deposition.
In addition, is a PCVCSEL""s eighth cladding-layer, which is constructed from a concentrically-graded P-doped (GaAlAs) xe2x80x9cGallium-Aluminum-Arsenidexe2x80x9d ternary material, and epitaxially deposited upon the top outermost surface of the last layer comprising the PCVCSEL""s fourth active-area (i.e., called pump 2).
In addition, is a PCVCSEL""s fifth contact-layer, which is comprised from a highly p+ doped (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d binary material, and epitaxially deposited upon the top outermost surface of the PCVCSEL""s eighth cladding-layer.
In addition, is a semi-reflecting quarterwave DBR mirror-stack assembly, which is made from a plurality of alternating layers, or more specifically a plurality of one or more layers of (SiO2) xe2x80x9cFused Silicaxe2x80x9d and one or more layers of (ZnO) xe2x80x9cZinc-Oxidexe2x80x9d. For example, a layer of (SiO2) xe2x80x9cFused Silicaxe2x80x9d is epitaxially deposited upon the top outermost surface of a PCVCSEL""s fifth and last contact-layer. Additionally, with a layer (ZnO) xe2x80x9cZinc-Oxidexe2x80x9d subsequently and epitaxially deposited upon the top outermost surface of the previously deposited (SiO2) xe2x80x9cFused Silicaxe2x80x9d layer; thereby, making a mirror pair of (SiO2/ZnO) reflectors.
Furthermore, if additional mirror-pairs are required, several more layers of additional mirror-pairs can be deposited upon the existing layers of (SiO2) xe2x80x9cFused Silicaxe2x80x9d and (ZnO) xe2x80x9cZinc-Oxidexe2x80x9d. The plurality of alternating layers that make-up a PCVCSEL""s quarterwave DBR mirror-stack assembly is formed from one mirror pair to ten mirror pairs, with a preferred number of mirror pairs ranging from four to five mirror pairs.
An additional object of the present invention is its ability to create phase-conjugated, convergent, distortion free (i.e., reversal of intracavity distortions like diffraction, divergence, and light-scattering), and collimated (i.e., plane-parallel phase fronts) laser output emissions. Accomplished, using what is called intracavity degenerative four-wave mixing (i.e., called four-wave mixing because there are four separate frequencies of phase-matched laser light involved in the phase-conjugate process that occurs within the present invention), which occurs within the thin nonlinear semiconductor materials used to construct a PCVCSEL""s double-heterostructure active-region diodes.
Moreover, the previously mentioned nonlinear semiconductor materials are naturally located at the center of a PCVCSEL""s vertical-cavity, where wave-fronts produced by the PCVCSEL""s two laser pumps (i.e., called Pump 1 and Pump 2) will intersect with wave-fronts produced by the PCVCSEL""s two laser probes (i.e., called Probe 1 and Probe 2) causing to form therein, small and large spatial interference-gratings, which will ultimately form within the PCVCSEL""s vertical-cavity what is sometimes called xe2x80x98a phase-conjugate mirrorxe2x80x99.
Furthermore, the semiconductor materials used in constructing a PCVCSEL""s vertical-cavity must exhibit a nonlinear property called xe2x80x9cthird-order susceptibilityxe2x80x9d, which is necessary for the production of a xe2x80x9cphase-conjugate mirrorxe2x80x9d. Additionally, materials that exhibit nonlinear third-order susceptibilities are not limited to semiconductors like (GaAs) xe2x80x9cGallium-Arsenidexe2x80x9d, (InAs) xe2x80x9cIndium-Arsenidexe2x80x9d, (InP) xe2x80x9cIndium-Phosphidexe2x80x9d, and (GaSb) xe2x80x9cGallium-Antimonidexe2x80x9d; binary semiconductor materials that have the Cubic crystal-symmetry of xe2x80x98class-F43mxe2x80x99 and a space-group of xe2x80x9c216xe2x80x9d.
Moreover, nonlinear third-order susceptibilities are also exhibited in photo-refractive materials like (KDP) xe2x80x9cPotassium-Dihydrogen-Phosphatexe2x80x9d, and (ADP) xe2x80x9cAmmonium-Dihydrogen-Phosphatexe2x80x9d; photo-refractive materials that have the Tetragonal crystal-symmetry of xe2x80x98class-142dxe2x80x99 and a space-group of xe2x80x9c122xe2x80x9d.
Therefore, photo-refractive materials exhibiting nonlinear third-order susceptibilities can also be deposited at the center of a PCVCSEL""s vertical-cavity and used as the nonlinear material that produces phase-conjugated, convergent, and distortion free laser output emissions.